阅读说明：本技术 一种高质量压电薄膜退火降温方法和制备方法 (High-quality piezoelectric film annealing and cooling method and preparation method ) 是由 张素伟 任玲玲 姚雅萱 金森林 李硕 于 2021-06-21 设计创作，主要内容包括：本发明实施例涉及压电材料技术领域,具体涉及一种高质量压电薄膜退火降温方法和制备方法。所述退火降温方法为在压电薄膜退火后包括第一段降温过程和第二段降温过程；所述第一段降温过程为在退火炉内以降温速率为0.5-1℃/s降温至第一温度；所述第二段降温过程为在退火炉内以2-3℃/s的降温速率从第一温度降温至第二温度。本发明通过控制退火后降温段数的降温速率、降温温度以及降温时长,使压电薄膜与衬底间由于热膨胀系数不同导致薄膜内部产生的应力得到缓慢释放,减少薄膜内部的裂纹,提升薄膜质量,进而降低漏电流,从而提升其电学性能。(The embodiment of the invention relates to the technical field of piezoelectric materials, in particular to a high-quality piezoelectric film annealing and cooling method and a preparation method. The annealing and cooling method comprises a first section of cooling process and a second section of cooling process after the piezoelectric film is annealed; the first stage of temperature reduction process is to reduce the temperature in the annealing furnace to a first temperature at the temperature reduction rate of 0.5-1 ℃/s; and the second stage of temperature reduction process is to reduce the temperature from the first temperature to the second temperature in the annealing furnace at the temperature reduction rate of 2-3 ℃/s. According to the invention, by controlling the cooling rate, the cooling temperature and the cooling duration of the number of cooling stages after annealing, the stress generated in the film due to different thermal expansion coefficients between the piezoelectric film and the substrate is slowly released, cracks in the film are reduced, the quality of the film is improved, and further the leakage current is reduced, so that the electrical performance of the film is improved.)

1. The annealing and cooling method for the high-quality piezoelectric film is characterized by comprising a first section of cooling process and a second section of cooling process after the piezoelectric film is annealed; the first stage of temperature reduction process is to reduce the temperature in the annealing furnace to a first temperature at the temperature reduction rate of 0.5-1 ℃/s; and the second stage of temperature reduction process is to reduce the temperature from the first temperature to the second temperature in the annealing furnace at the temperature reduction rate of 2-3 ℃/s.

2. The method according to claim 1, wherein the first temperature is 300 ℃.

3. The method of claim 1, wherein the second temperature is 25 ℃.

4. A method for preparing a high-quality piezoelectric thin film, which comprises the annealing and cooling method according to any one of claims 1 to 3.

5. The method for preparing a high-quality piezoelectric thin film according to claim 4, further comprising the steps of substrate treatment, spin coating to deposit the thin film, drying, pyrolysis and annealing which are sequentially performed before the step of annealing and cooling.

6. The method for preparing a high-quality piezoelectric thin film according to claim 4, wherein the substrate treatment is cleaning and drying of the surface of the substrate with ethanol.

7. The method for preparing a high-quality piezoelectric thin film according to claim 4, wherein the spin-coating deposition of the thin film is performed by spin-coating the sol on the processed substrate for 10s at a rotation speed of 400-700 rpm on a spin coater after the sol is sucked by a pinhole injector, and then for 20-50 s at a rotation speed of 3000-5000 rpm.

8. The method for preparing a high-quality piezoelectric thin film according to claim 4, wherein the annealing is carried out at 600-900 ℃ for 250-450 s.

9. The method for preparing a high-quality piezoelectric thin film according to claim 4, wherein the steps of spin coating to deposit a thin film, drying, pyrolyzing, annealing and cooling are repeated until a piezoelectric thin film with a desired thickness is obtained.

10. A high-quality piezoelectric thin film, which is prepared by the method for preparing a high-quality piezoelectric thin film according to any one of claims 4 to 9.

Technical Field

The invention relates to the technical field of piezoelectric materials, in particular to a high-quality piezoelectric film annealing and cooling method and a preparation method.

Background

With the rapid development of electronic components toward multi-functionalization, miniaturization, high sensitivity and greening, piezoelectric thin films gradually become irreplaceable important components of various micro-drivers and sensors. Therefore, the piezoelectric thin film has received a great deal of attention in both basic research and application research.

Piezoelectric ceramics are a promising functional material, but compared with the research of ceramic bulk materials, the research of thin film materials is relatively lagged, so that the development of high-performance piezoelectric thin films is very important. Common methods for preparing piezoelectric thin films include physical vapor deposition, chemical liquid deposition, and the like. The sol-gel method in the chemical vapor deposition method has attracted extensive attention due to the advantages of low preparation cost, simple operation, easy industrialization, no toxic and harmful substances and the like. The sol-gel method is that metal alkoxide containing certain ion proportion and other organic or inorganic metal salt are dissolved in a common solution, a uniform precursor-sol is formed through hydrolysis and polymerization, the sol is coated on a substrate through the modes of pulling, spin coating, deposition and the like, then drying treatment is carried out, and finally annealing treatment is carried out to obtain the piezoelectric film. However, in this production method, a large amount of residual stress generated inside the thin film causes cracks inside the thin film due to the difference in thermal expansion coefficient between the substrate and the thin film. And as the thickness of the film increases, the probability of internal cracks of the film is increased due to the increase of internal defects, so that the quality of the piezoelectric film is poor.

The information disclosed in this background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.

Disclosure of Invention

Object of the Invention

In order to solve the main problems and defects of the piezoelectric film in the prior art, the invention aims to provide a high-quality piezoelectric film annealing and cooling method and a preparation method. The invention adopts a segmented cooling mode after annealing, and improves the quality and performance of the piezoelectric film by controlling the cooling rate of the number of cooling segments and the cooling time of the cooling temperature.

Solution scheme

In order to achieve the purpose of the invention, the embodiment of the invention provides the following technical scheme:

in a first aspect, the invention provides a high-quality piezoelectric film annealing and cooling method, wherein the annealing and cooling method comprises a first section of cooling process and a second section of cooling process after the piezoelectric film is annealed; the first stage of temperature reduction process is to reduce the temperature in the annealing furnace to a first temperature at the temperature reduction rate of 0.5-1 ℃/s; and the second stage of temperature reduction process is to reduce the temperature from the first temperature to the second temperature in the annealing furnace at the temperature reduction rate of 2-3 ℃/s.

In one possible implementation, the first temperature is 300 ℃.

In one possible implementation, the second temperature is 25 ℃.

In a second aspect, the invention provides a method for preparing a high-quality piezoelectric thin film, wherein the method for preparing the high-quality piezoelectric thin film comprises the annealing and cooling method.

In a possible implementation manner, the preparation method further comprises the steps of substrate treatment, spin coating to deposit a film, drying, pyrolysis and annealing which are sequentially carried out before the step of annealing and cooling.

In one possible implementation, the substrate processing is cleaning and drying the surface of the substrate by using ethanol.

In a possible implementation manner, the spin-coating deposition film is to spin-coat the sol for 10s at a rotation speed of 400-700 rpm by using a spin coater after the sol is absorbed by a pinhole injector, and then spin-coat for 20-50 s at a rotation speed of 3000-5000 rpm, and spin-coat the sol on the processed substrate.

In one possible implementation, the drying is drying at 200 ℃ for 120 s.

In one possible implementation mode, the pyrolysis is pyrolysis at 300-600 ℃ for 200-400 s.

In one possible implementation mode, the annealing is carried out at the temperature of 600-900 ℃ for 250-450 s.

In one possible implementation, the steps of spin coating to deposit the thin film, drying, pyrolysis, annealing and annealing cooling are repeated until the piezoelectric thin film with the required thickness is obtained.

In a third aspect, the invention provides a high-quality piezoelectric film, which is prepared by the preparation method of the high-quality piezoelectric film.

Advantageous effects

The annealing and cooling method for the high-quality piezoelectric film provided by the invention adopts a sectional cooling mode, and by controlling the cooling rate, the cooling temperature and the cooling duration of the number of cooling sections after annealing, the stress generated in the film due to different thermal expansion coefficients between the piezoelectric film and the substrate is slowly released, the cracks in the film are reduced, the quality of the film is improved, and the leakage current is reduced, so that the electrical performance of the film is improved. And the quality of the piezoelectric film is obviously improved by prolonging the cooling time after annealing.

The preparation method of the high-quality piezoelectric film provided by the invention is simple and feasible and has lower cost. Compared with the piezoelectric film obtained by the conventional preparation method, the piezoelectric coefficient of the piezoelectric film obtained by the invention is greatly improved, and the quality performance is excellent.

Drawings

FIG. 1 is a surface topography of a piezoelectric film of examples 1 to 3;

FIG. 2 is a surface topography of the piezoelectric films of comparative examples 1-3.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are a part of the embodiments of the present invention, but not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Furthermore, in the following detailed description, numerous specific details are set forth in order to provide a better understanding of the present invention. It will be understood by those skilled in the art that the present invention may be practiced without some of these specific details. In some instances, materials, methods, means, and the like that are well known to those skilled in the art have not been described in detail in order to not unnecessarily obscure the present invention.

Throughout the specification and claims, unless explicitly stated otherwise, the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element or component but not the exclusion of any other element or component.

The substrate treatment, spin coating to deposit thin film, drying and pyrolysis steps in the examples and comparative examples of the present invention are all the same.

Example 1.

A high-quality piezoelectric film is prepared by the following method:

(1) substrate processing, spin coating and film deposition, drying, pyrolysis and annealing; the substrate treatment comprises the steps of cleaning and drying the surface of a Pt/Ti/SiO 2/Si/substrate by adopting ethanol; the spin-coating deposition film is to spin-coat the sol on a spin coater at the rotating speed of 500rpm for 10s and then at the rotating speed of 5000rpm for 30s after the sol is absorbed by a pinhole injector, and spin-coat the sol on a processed substrate; the drying is drying at 200 ℃ for 120 s; the pyrolysis is pyrolysis at 300 ℃ for 200 s; the annealing is carried out for 300s at 750 ℃;

(2) cooling the annealed film sample, and cooling the annealing furnace to 300 ℃ at the speed of 0.5 ℃/s; then cooling the annealing furnace from 300 ℃ to 25 ℃ at the cooling rate of 2 ℃/s;

(3) and taking out the piezoelectric film sample from the annealing furnace to obtain the piezoelectric film.

Example 2.

A high-quality piezoelectric film is prepared by the following method:

(1) substrate processing, spin coating and film deposition, drying and pyrolysis; the concrete steps are the same as example 1;

(2) cooling the annealed film sample, and cooling the annealing furnace to 300 ℃ at the speed of 0.5 ℃/s; then cooling the annealing furnace from 300 ℃ to 25 ℃ at a cooling rate of 3 ℃/s;

(3) and taking out the piezoelectric film sample from the annealing furnace to obtain the piezoelectric film.

Example 3.

A high-quality piezoelectric film is prepared by the following method:

(1) substrate processing, spin coating and film deposition, drying and pyrolysis; the concrete steps are the same as example 1;

(2) cooling the annealed film sample, and cooling the annealing furnace to 300 ℃ at the speed of 1 ℃/s; then cooling the annealing furnace from 300 ℃ to 25 ℃ at a cooling rate of 3 ℃/s;

(3) and taking out the piezoelectric film sample from the annealing furnace to obtain the piezoelectric film.

Comparative example 1.

A piezoelectric film is prepared by the following method:

(1) substrate processing, spin coating and film deposition, drying and pyrolysis; the concrete steps are the same as example 1;

(2) cooling the annealed film sample to 25 ℃ at the speed of 10 ℃/s;

(3) and taking out the piezoelectric film sample from the annealing furnace to obtain the piezoelectric film.

Comparative example 2.

A piezoelectric film is prepared by the following method:

(1) substrate processing, spin coating and film deposition, drying and pyrolysis; the concrete steps are the same as example 1;

(2) cooling the annealed film sample to 400 ℃ at the speed of 1 ℃/s; then cooling the annealing furnace from 400 ℃ to 25 ℃ at a cooling rate of 10 ℃/s;

(3) and taking out the piezoelectric film sample from the annealing furnace to obtain the piezoelectric film.

Comparative example 3.

A piezoelectric film is prepared by the following method:

(1) substrate processing, spin coating and film deposition, drying and pyrolysis; the concrete steps are the same as example 1;

(2) cooling the annealed film sample, and cooling the annealing furnace to 300 ℃ at the speed of 20 ℃/s; then cooling the annealing furnace from 300 ℃ to 25 ℃ at a cooling rate of 10 ℃/s;

(3) and taking out the piezoelectric film sample from the annealing furnace to obtain the piezoelectric film.

Data comparison

Surface topography

After the surface gold spraying was performed on the piezoelectric thin films obtained in examples 1 to 3 and comparative examples 1 to 3, the surface morphology of each piezoelectric thin film was measured using a scanning electron microscope, as shown in fig. 1 and 2, respectively. Fig. 1a is a surface topography of a piezoelectric thin film of example 1, fig. 1b is a surface topography of a piezoelectric thin film of example 2, fig. 1c is a surface topography of a piezoelectric thin film of example 3, fig. 2a is a surface topography of a piezoelectric thin film of comparative example 1, fig. 2b is a surface topography of a piezoelectric thin film of comparative example 2, and fig. 2c is a surface topography of a piezoelectric thin film of comparative example 3. As can be seen from FIG. 1, the piezoelectric thin films of examples 1 to 3 had uniform and dense surfaces and no cracks. As can be seen from fig. 2, the piezoelectric thin film of comparative example 1 had pores and was not uniform in surface, the piezoelectric thin film of comparative example 2 had pores and cracks and was uniform in surface, and the piezoelectric thin film of comparative example 3 had pores and cracks.

Second, piezoelectric coefficient

After plating platinum electrodes on the surfaces of the piezoelectric films obtained in examples 1 to 3 and comparative examples 1 to 3, the piezoelectric coefficients thereof were measured using a laser doppler vibrometer. The piezoelectric coefficient of the piezoelectric film of example 1 was 58pm/V, the piezoelectric coefficient of the piezoelectric film of example 2 was 57pm/V, the piezoelectric coefficient of the piezoelectric film of example 3 was 55pm/V, the piezoelectric coefficient of the piezoelectric film of comparative example 1 was 27pm/V, the piezoelectric coefficient of the piezoelectric film of comparative example 2 was 35pm/V, and the piezoelectric coefficient of the piezoelectric film of comparative example 3 was 31 pm/V.

Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.